Malleable cannula

ABSTRACT

A malleable cannula has a body with a proximal end and a distal end, the body having a wall defining a lumen extending from the proximal end to the distal end. A reinforcement member extends along the lumen, the reinforcement member having an interior side facing the lumen and an exterior side facing away from the lumen. A malleable member extends along a portion of the exterior side of the reinforcement member. The malleable member may be constructed of a tube with a wire slidably received within the tube and may include an anchor.

FIELD OF THE INVENTION

[0001] The present invention relates to a medical cannula. Inparticular, the present invention relates to a malleable venous cannulaused to drain blood from the heart during heart surgery.

BACKGROUND OF THE INVENTION

[0002] During cardiac surgery, circulation of blood through a patient'sbody may be maintained by connecting the patient to an extracorporealsystem, such as a heart-lung machine. The heart-lung machine adds oxygento and removes carbon dioxide from the blood, heats or cools the blood,and provides impetus to the blood to cause the blood to circulatethrough the patient's vascular system.

[0003] Connecting a patient to a extracorporeal system is typically doneby inserting a cannula into the patient's venous system near or in theheart to remove blood from the patient and direct it to theextracorporeal circuit. After the blood has passed through theextracorporeal circuit, the blood is infused into the patient's arterialsystem near the heart.

[0004] The venous cannula that is inserted into the heart to siphonblood away for entry into the heart-lung machine is typically insertedinto the right atrium and/or vena cava. The venous cannula may be asingle stage device having one set of input apertures or a two-stagedevice used to simultaneously drain the right atrium and superior venacava through an atrial basket while the inferior vena cava is drainedthrough another set of apertures at the distal tip of the cannula.Oxygenated blood is returned to the heart from the heart-lung machineusing an arterial cannula to return blood to the aorta.

[0005] In order to maintain proper blood flow rate through a cannula,the cannula body typically has a wire support, such as a helicalreinforcement spring to prevent kinking or other degradation of thelumen extending through the cannula body. Additionally, it is oftendesired to have a malleable cannula that may be bent into a particularconfiguration and that maintains the chosen configuration during use.Such malleability may be provided by the inclusion of a malleablemember, such as a relatively stiff wire extending along the length ofthe cannula body, the malleable member maintaining the cannula in aparticular shape chosen by the surgeon.

[0006] The construction of a suitable malleable cannula presents certaindesign challenges. The addition of a malleable member may compromise thecross-sectional area of the lumen, thus degrading the flow rate providedby a particular size cannula. For example, a cannula having a particularoutside diameter may have a 25-35 percent reduction in flow through thelumen when a malleable member is added to the design. Accordingly, toachieve the same flow rate, a cannula having a larger outside diametermay need to be chosen, which may not be desirable given the largeraperture necessary for insertion of the larger cannula into a particularportion of the heart.

[0007] Another design issue that arises with respect to the addition ofa malleable member to a cannula is the issue of how to anchor themalleable member within the cannula body. Although a cannula istypically molded of a plastic material that will help to keep amalleable wire in place, when the cannula body is bent and twisted in avariety of directions by the surgeon during use, the wire may shift inthe cannula body due to the changing curvature of the outer wall of thecannula. Further, movement of the malleable wire with respect to thecannula wall may result in damage to the cannula wall by the wire andthe possible puncture of the cannula wall by the wire under certaincircumstances.

[0008] There is a need for a cannula that is malleable but does not havea reduction in the flow rate for a given size cannula. Further, there isa need for a method and apparatus for improved anchoring of a malleablemember within a cannula body. Further, there is a need for malleablemember that is configured to not permit damage to the cannula wall bymovement of the malleable member when the cannula is shaped during use.

[0009] It would be desirable to provide a system and/or method thatprovides one or more of these or other advantageous features. Otherfeatures and advantages will be made apparent from the presentspecification. The teachings disclosed herein extend to thoseembodiments that fall within the scope of the appended claims,regardless of whether they accomplish one or more of the aforementionedneeds.

SUMMARY OF THE INVENTION

[0010] The invention relates to a malleable cannula. The malleablecannula has a body with a proximal end and a distal end, the body havinga wall defining a lumen extending from the proximal end to the distalend. A reinforcement member extends along the lumen, the reinforcementmember having an interior side facing the lumen and an exterior sidefacing away from the lumen. A malleable member extends along a portionof the exterior side of the reinforcement member, the malleable memberadapted to retain the body in a custom shape after the body is bent intothe custom shape and includes a tube and a wire slidably received withinthe tube.

[0011] The invention further relates to a malleable cannula having abody with a proximal end and a distal end, the body having a walldefining a lumen extending from the proximal end to the distal end. Areinforcement spring extends along the lumen, the reinforcement springhaving an interior side facing the lumen and an exterior side facingaway from the lumen. A malleable member extends along at least a portionof the exterior side of the reinforcement spring, the malleable memberadapted to retain the body in a custom shape after the body is bent intothe custom shape. The malleable cannula further includes means foranchoring the malleable member within the wall, the means for anchoringlimiting the travel of the malleable member with respect to the wallwhen the cannula is manipulated.

[0012] The invention further relates to a malleable cannula having abody with a wall with an annular cross-section defining a lumenextending from a proximal portion of the body to a distal portion of thebody. A reinforcement spring extends along a portion of the lumen. Amalleable member is incorporated into the wall, the malleable memberhaving a first portion and an anchor attached to and extending from thefirst portion, the anchor adapted to substantially inhibit movement ofthe malleable member within the wall.

[0013] Further still, the invention relates to a method of making amalleable cannula. The method includes the steps of providing a mandreland a quantity of molten plastic material, dipping the mandrel in theplastic material to coat the mandrel with a first layer of the plasticmaterial, and curing the first layer. The method further includes thesteps of sliding a reinforcement spring over the first layer, providinga malleable member having an anchor at a distal end thereof, couplingthe malleable member to the exterior side of the reinforcement spring,and dipping the mandrel into the plastic material to coat the mandrelwith a second layer of the plastic material.

[0014] The invention further relates to a malleable cannula having abody with a proximal end and a distal end, the body having a walldefining a lumen extending from the proximal end to the distal end. Thecannula further includes a reinforcement spring extending along thelumen, the reinforcement spring having an interior side facing the lumenand an exterior side facing away from the lumen. A malleable wireextends along the exterior side of the reinforcement spring, themalleable wire having a U-shape, the lower portion of the U-shapedisposed at the distal end of the body.

[0015] Even further still, the invention relates to a malleable cannulahaving a body with a proximal end and a distal end, the body having awall defining a lumen extending from the proximal end to the distal end.A reinforcement spring extends along the lumen and a malleable wireextends along the exterior side of the reinforcement spring, thereinforcement spring having a plurality of loops, each loop having anoutwardly bowed portion shaped to accommodate the malleable wire betweenthe reinforcement spring and the lumen without impacting thecross-sectional area of the lumen.

[0016] The invention is capable of other embodiments and of beingpracticed or being carried out in various ways. Alternative exemplaryembodiments relate to other features and combinations of features as maybe generally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will become more fully understood from thefollowing detailed description, taken in conjunction with theaccompanying drawings, wherein like reference numerals refer to likeelements, in which:

[0018]FIG. 1 is a front elevation view of a cannula;

[0019]FIG. 2 is an enlarged perspective view of a segment of the distalend of a cannula according to a first embodiment of the invention, thesegment location generally indicated by line 2-2 of FIG. 1;

[0020]FIG. 3 is a sectional view taken generally along line 3-3 of FIG.2;

[0021]FIG. 4 is an enlarged perspective view of a segment of the distalend of a cannula according to a second embodiment of the invention, thesegment location generally indicated by line 2-2 of FIG. 1;

[0022]FIG. 5 is a sectional view taken generally along line 5-5 of FIG.4;

[0023]FIG. 6 is an enlarged perspective view of a segment of a distalend of a cannula according to a third embodiment of the invention, thesegment location generally indicated by line 2-2 of FIG. 1;

[0024]FIG. 7 is a sectional view taken generally along line 7-7 of FIG.6;

[0025]FIG. 8 is an enlarged perspective view of a segment of the distalend of a cannula according to a fourth embodiment of the invention, thesegment location generally indicated by line 2-2 of FIG. 1;

[0026]FIG. 9 is a sectional view taken generally along line 9-9 of FIG.8;

[0027]FIG. 10 is an enlarged perspective view of a segment of the distalend of a cannula according to a fifth embodiment of the invention, thesegment location generally indicated by line 2-2 of FIG. 1; and

[0028]FIG. 11 is a sectional view of a cannula body according to a sixthembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] Referring to FIG. 1, a catheter or cannula, shown as, but notlimited to, venous cannula 10 has a proximal end 12 and a distal end 14.A tip 16 is located at the distal end 14 of the cannula 10 and a lumen18 defined by a wall 20 extends through the cannula 10 from the proximalend 12 to the tip 16.

[0030] The lumen 18 may be open at the proximal end 12 to be connectedto a cardiac bypass system such as a heart-lung machine. When cannula 10is a venous cannula, the tip 16 includes a number of apertures 22 fordraining blood from the heart to pass through the lumen 18 and into aheart-lung machine. Various methods of performing a cardiopulmonarybypass are known in the art. In the embodiment depicted in FIG. 1, thecannula is a single stage venous cannula having set of apertures 22located at the distal end 14. In other embodiments, the cannula may be adual stage venous cannula having two sets of apertures used to drain twoportions of the heart simultaneously.

[0031] Referring to FIGS. 1 and 2, a reinforcement member, shown ashelical reinforcement spring 24 may extend over a substantial portion ofthe length of cannula 10 to prevent kinking or closing off of the lumen18 when the device is in use by a surgeon. In an exemplary embodiment, amalleable member 30 may extend along the length of reinforcement spring24. Malleable member 30, like reinforcement spring 24, is embeddedwithin wall 20.

[0032] A surgeon or other user may bend the cannula 10 into a desiredshape by hand pressure. The malleable member 30 maintains the cannula inthe bent shape chosen by the surgeon. The cannula may be bent again fromthe first desired shape into a second desired shape by hand pressure ifthat is deemed necessary, and the malleable member 30 will maintain thesecond desired shape. The bending of the cannula may be performed whilefluid (e.g. blood) is flowing through the lumen 18 without interruptingthe flow of fluid. Accordingly, the cannula may be shaped and reshapedduring a surgical procedure while flood is flowing through the cannulawithout interruption of the surgical procedure. Bending or shaping ofone portion of the cannula may be performed without altering the shapeof other portions of the cannula.

[0033] When the cannula 10 is used as a venous cannula, the malleabilitydiscussed above is useful, especially where the surgeon desires a bendin the distal end 14 of the cannula (e.g. within 10 cm of the tip 16) toaid in the proper placement of the cannula within the heart. Forexample, the surgeon may desire to insert the cannula into an aperturein the right atrium of the heart and have a bend in the distal end 14 ofthe cannula to direct the tip 16 either up into the superior vena cavaor down into the inferior vena cava. The cannula of the presentinvention may be used to replace a cannula having a permanent bend inthe distal end. The use of a malleable cannula to permit a custom bendin the distal end of the cannula may be desirable when placing a patienton cardiopulmonary bypass prior to performing mitral or aortic valvereplacement or repair.

[0034] Another reason for providing a malleable member 30 in the cannula10 relates to improving the usage of space. A surgeon may wish to bendthe cannula 10 to avoid interference with other surgical tools near theaperture into a patient's body. This is especially the case whenperforming minimally invasive surgical procedures having limited accessspace into the patient.

[0035] The malleable member 30 may extend over a substantial portion ofthe length of cannula 10, or may only extend along a particular portionfor which malleability is desired. For example, in one embodiment, themalleable member 30 may extend over a portion (e.g. 15 cm) of the distalend of the cannula 10, to provide malleability to that portion, whilethe rest of the cannula remains resilient.

[0036] Referring to FIG. 2, in an exemplary embodiment, malleable member30 includes a tube 32 that is formed into an anchor, shown as collar 34at the distal end of the tube 32. In one embodiment, a wire 36 may beplaced in tube 32 to provide additional support in maintaining cannula10 in any particular shape chosen by the surgeon.

[0037] Collar 34 anchors malleable member 30 into place within wall 20such that when cannula 10 is bent, twisted, and otherwise manipulated bya surgeon, malleable member 30 remains in place rather than slidingwithin wall 20, which can lead to undesired damage to wall 20. Collar 34may be prevented from sliding toward proximal end 12 by the material inwall 20 as well as by direct interference with the distal end of thereinforcement spring 24.

[0038] Further referring to FIG. 2, the location of tube 32 on theexterior of reinforcement spring 24 results in a configuration that doesnot degrade the flow through lumen 18. Accordingly, for a cannula havinga given outside diameter, the cross-sectional area of the lumen may bethe same for both a cannula having a malleable member and one without.

[0039] Referring to FIG. 3, in a preferred embodiment, wire 36 extendsthrough tube 32 up to the point at which tube 32 narrows to form collar34. Collar 34 is a flattened portion of tube 32. Wire 36 and tube 32 aresized to permit easy insertion of wire 36 into tube 32 during theconstruction of cannula 10.

[0040] Referring to FIG. 4, in another exemplary embodiment, the distalend of tube 32 may be flattened and formed into an anchor, shown as ahook 38 that wraps around the last few coils of the reinforcement spring24. The hook 38, like the collar 34 shown in FIGS. 2 and 3, maintainsmalleable member 30 in place within wall 20 as the cannula 10 ismanipulated by the surgeon.

[0041] Referring to FIG. 5, wire 36 extends through tube 32 to providesupport to the malleable member 30. Wire 36 terminates at the locationthat tube 32 narrows to form hook 38. Hook 38 is shown as wrappingaround the final four coils of reinforcement spring 24 but may wraparound fewer or more coils as desired or to provide additional anchoringof malleable member 30. The reinforcement spring 24 prevents malleablemember 30 from shifting to the left in the reference frame of FIG. 5 andthe material of wall 20 prevents malleable member 30 from shifting tothe right, so the combination of reinforcement spring 24 and wall 20anchors malleable member 30 into place.

[0042] Referring to FIGS. 6 and 7, in another exemplary embodiment ofthe invention, the distal end of malleable member 30 is flattened intoan anchor, shown as a stepped portion having an upper step 40 and alower step 42. The lower step may be tucked underneath the last fewcoils of reinforcement spring 24 in order to anchor malleable member 30into place. The stepped portion therefore interlocks with thereinforcement spring 24 to anchor malleable member into place while thecannula is manipulated by the surgeon. As depicted in FIG. 7, in anexemplary embodiment, wire 36 extends through tube 32 up to the point atwhich the stepped portion begins. Preferably, the stepped portion isformed by flattening tube 32 without the wire 36 disposed therein.

[0043] Further referring to FIGS. 6 and 7, in contrast with theembodiments depicted in FIGS. 2-5, the lower step 42 is located on thelumen side of reinforcement spring 24. The number of coils that lowerstep 42 extends underneath is a design choice based upon the degree ofdesired anchoring and other considerations. The location of lower stepon the interior side of reinforcement spring 24 has little effect on thecross-sectional area of lumen 18 due to the flattened design of theanchor.

[0044] Referring to FIGS. 8 and 9, in another exemplary embodiment ofthe invention, malleable member 30 may comprise a looped wire 44. Thelooped wire 44 is anchored into position with respect to wall 20 due tothe fact that the material of wall 20 surrounds the distal end of loopedwire 44, thus preventing substantial movement of looped wire 44 withinwall 20.

[0045] Referring to FIG. 10, in another exemplary embodiment of theinvention, malleable member 30 may include wire 36 slidably disposedwithin tube 32 and extending outwardly therefrom at the distal end ofmalleable member 30. Accordingly, a slip joint 46 is arranged at thepoint at which wire 36 enters tube 30 at the distal end. When a surgeonmanipulates the cannula, the wire 36 may slide through slip joint 46into tube 32 to relieve stress on the end 48 of wire 36 such that theend 48 is not forced through the material of wall 20, thus possiblydamaging wall 20. In the embodiment of FIG. 10, the construction ofmalleable member 30 is such that stress is relieved through the relativesliding of wire 36 and tube 32 such that malleable member 30 need not besolidly anchored with respect to wall 20 as in the embodiments depictedin FIGS. 2-8.

[0046] Referring to FIG. 11, in another exemplary embodiment of theinvention, the reinforcement spring 24 may be shaped to create extraroom such that malleable member 30 may be disposed on the interior sideof reinforcement spring 24 without negatively impacting thecross-sectional area of lumen 18. In the embodiment of FIG. 11,malleable member 30 may be made of a single solid wire.

[0047] A cannula, such as that depicted in FIG. 1, may be made byproviding a stainless steel mandrel and dipping it into a plasticmaterial, such as liquid plastisol. The initial layer of plastisol maythen be cured (at least partially) in an oven. The reinforcement spring24 (with or without the malleable member coupled thereto) may then beslipped over the first layer of plastisol (with the mandrel still inplace underneath the initial layer of plastisol). If added separately,the malleable member may then placed on the exterior of thereinforcement spring through the use of a small amount of liquidplastisol to “weld” the malleable member into place.

[0048] In the embodiments of FIGS. 4 and 6, the anchor (i.e. the hook orstepped portion) may aid in maintaining the placement of the malleablemember over the reinforcement spring before the next layer of plastisolis applied. Once the reinforcement spring and malleable member are inplace, the mandrel is again dipped into liquid plastisol to add anotherlayer of wall material, a step that is performed as many additionaltimes as necessary to create the desired wall thickness. It may bedesirable to only partially cure the individual layers before addingadditional layers to provide for additional adhesion between adjacentlayers. Once the cannula construction is complete, the layers may befully cured. Pressurized alcohol is then typically injected to releasethe finished cannula from the mandrel.

[0049] Other methods of cannula construction are known in the art. Forexample, another method of making a cannula according to an embodimentof the present invention is to utilize a series of layers of extrudedtubing. The reinforcement spring and malleable member may be addedbetween adjacent layers of the tubing, which are slidably added duringconstruction of the cannula.

[0050] The materials used to construct the different cannula embodimentsdisclosed herein are generally known in the art. For example, theplastisol used to form the wall in the dip molding process describedabove is a liquid vinyl dispersion that is fused by heat to form a solidend product. Other plastic materials may also be suitable. Thereinforcement spring is typically made of stainless steel as are theparts of the malleable member. In a preferred embodiment, the tube ofthe malleable member is made of 304 stainless steel while the wireinserted within the tube (in those embodiments having such a structure)is made of 302 stainless steel.

[0051] The collar, hook, and stepped anchors at the distal end of themalleable member depicted in FIGS. 2, 4, and 6 are made, in an exemplaryembodiment, by flattening and shaping the end portion of the hollow tube32. This method of construction alleviates work hardening concerns andother materials difficulties that occur when shaping a solid stainlesssteel wire into the anchor forms. A large amount of compressive force isrequired to shape a solid wire into an anchor, while a tube may beflattened and shaped much more easily, without resulting in thebrittleness that results from work hardening. Further, flattening thetube to create the various anchors eliminates the pointed end of thewire or tube that may otherwise present an increased risk of damage tothe cannula wall.

[0052] When using the wire and tube construction of the malleablemember, the distal end of the tube is first flattened and formed intothe desired shape. The wire is then inserted into the tube to providethe desired rigidity and mass to malleable member 30. The tube 32 issized to slidably receive wire 36 during the construction process.

[0053] While the detailed drawings and specific examples given describevarious exemplary embodiments, they serve the purpose of illustrationonly. It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangements ofcomponents set forth in the preceding description or illustrated in thedrawings. For example, while a venous cannula is shown incorporating thevarious aspects of the invention, the invention may also be applicableto arterial cannulae, cardioplegia cannulae, or other cannula andcatheter designs that are intended to be malleable. Such cannulae areavailable in many sizes and shapes and used in different types ofsurgical procedures. Furthermore, other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangements of the exemplary embodiments without departing from thescope of the invention as expressed in the appended claims.

What is claimed is:
 1. A malleable cannula, comprising: a body having aproximal end and a distal end, the body having a wall defining a lumenextending from the proximal end to the distal end; a reinforcementmember extending along the lumen, the reinforcement member having aninterior side facing the lumen and an exterior side facing away from thelumen; and a malleable member extending along a portion of the exteriorside of the reinforcement member, the malleable member adapted to retainthe body in a custom shape after the body is bent into the custom shapeand comprising a tube and a wire slidably received within the tube. 2.The malleable cannula of claim 1, further comprising an anchor on adistal end of the malleable member, the anchor adapted to maintain theplacement of the malleable member within the wall.
 3. The malleablecannula of claim 2, wherein the malleable member has a generallycircular cross-section except for the anchor, which is a flattenedportion of the tube.
 4. The malleable cannula of claim 2, wherein theanchor comprises a hook that wraps around a distal end of thereinforcement member.
 5. The malleable cannula of claim 4, wherein thereinforcement member is a helical spring encased in the wall.
 6. Themalleable cannula of claim 5, wherein the hook wraps around at leastthree coils of the helical spring.
 7. The malleable cannula of claim 4,wherein the hook is flattened with respect to the rest of the malleablemember.
 8. The malleable cannula of claim 2, wherein the anchorcomprises a collar, the collar encased in the wall and substantiallyencircling the lumen.
 9. The malleable cannula of claim 8, wherein thecollar abuts the reinforcement member, thus aiding in maintaining theplacement of the malleable member.
 10. The malleable cannula of claim 2,wherein the anchor comprises a stepped portion interlocked with thereinforcement member.
 11. The malleable cannula of claim 10, wherein thestepped portion is a flattened strip of metal.
 12. The malleable cannulaof claim 10, wherein the reinforcement member is a helical springencased in the wall.
 13. The malleable cannula of claim 12, wherein thestepped portion extends between a pair of coils of the helical springand further includes an end portion extending underneath a plurality ofcoils of the helical spring.
 14. The malleable cannula of claim 13,wherein the wire extends through a portion of the tube that does notinclude the stepped portion.
 15. The malleable cannula of claim 1,wherein the cannula is a venous cannula.
 16. A malleable cannula,comprising: a body having a proximal end and a distal end, the bodyhaving a wall defining a lumen extending from the proximal end to thedistal end; a reinforcement spring extending along the lumen, thereinforcement spring having an interior side facing the lumen and anexterior side facing away from the lumen; a malleable member extendingalong at least a portion of the exterior side of the reinforcementspring, the malleable member adapted to retain the body in a customshape after the body is bent into the custom shape; and a means foranchoring the malleable member within the wall, the means for anchoringlimiting the travel of the malleable member with respect to the wallwhen the cannula is manipulated.
 17. The malleable cannula of claim 16,wherein the malleable member comprises a tube enclosing a wire, and themeans for anchoring is a flattened portion of the tube not having a wireextending therein.
 18. The malleable cannula of claim 17, wherein thetube and the wire are made of stainless steel.
 19. The malleable cannulaof claim 16, wherein the means for anchoring comprises a hook that wrapsaround a distal end of the reinforcement spring.
 20. The malleablecannula of claim 16, wherein the means for anchoring comprises a collar,the collar encased in the wall and substantially encircling the lumen.21. The malleable cannula of claim 16, wherein the means for anchoringcomprises a stepped portion interlocked with the reinforcement spring.22. The malleable cannula of claim 21, wherein the stepped portionextends between a pair of coils of the reinforcement spring and includesan end portion extending underneath a plurality of coils of thereinforcement spring.
 23. The malleable cannula of claim 16, wherein thecannula is a venous cannula.
 24. The malleable cannula of claim 16,further comprising a tip attached to the distal end of the body, the tiphaving a plurality of apertures interconnected with the lumen.
 25. Amalleable cannula, comprising: a body having a wall with an annularcross-section defining a lumen extending from a proximal portion of thebody to a distal portion of the body; a reinforcement spring extendingalong a portion of the lumen; and a malleable member incorporated intothe wall, the malleable member having a first portion and an anchorattached to and extending from the first portion, the anchor adapted tosubstantially inhibit movement of the malleable member within the wall.26. The malleable cannula of claim 25, wherein the malleable memberextends along an exterior side of the reinforcement spring.
 27. Themalleable cannula of claim 25, wherein the malleable member has agenerally circular cross-section except for the anchor, which isflattened.
 28. The malleable cannula of claim 25, wherein the malleablemember comprises a wire in a tube.
 29. The malleable cannula of claim25, wherein the malleable member is made of stainless steel.
 30. Themalleable cannula of claim 25, wherein the anchor comprises a hookwrapped around a distal end of the reinforcement spring.
 31. Themalleable cannula of claim 30, wherein the malleable member extendsalong a portion of the lumen on an exterior side of the reinforcementspring except for the wrapped hook portion.
 32. The malleable cannula ofclaim 30, wherein the hook wraps around at least three coils of thereinforcement spring.
 33. The malleable cannula of claim 25, wherein theanchor comprises a collar encased in the wall and substantiallyencircling the lumen.
 34. The malleable cannula of claim 33, wherein themalleable member comprises a wire in a tube.
 35. The malleable cannulaof claim 34, wherein the wire extends through a portion of the tube thatdoes not include the collar.
 36. The malleable cannula of claim 35,wherein the malleable member extends along an exterior side of thereinforcement spring.
 37. The malleable cannula of claim 25, wherein theanchor comprises a stepped portion interlocked with the reinforcementspring.
 38. The malleable cannula of claim 37, wherein the malleablemember extends along an exterior side of the reinforcement spring 39.The malleable cannula of claim 38, wherein the stepped portion extendsbetween a pair of coils of the reinforcement spring and further includesan end portion extending underneath a plurality of coils of thereinforcement spring.
 40. The malleable cannula of claim 25, wherein thecannula is a venous cannula.
 41. The malleable cannula of claim 25,further comprising a tip having a plurality of apertures interconnectedwith the lumen.
 42. A method of making a malleable cannula, comprisingthe steps of: providing a mandrel and a quantity of a molten plasticmaterial; dipping the mandrel into the plastic material to coat themandrel with a first layer of the plastic material; sliding areinforcement spring over the first layer; providing a malleable memberhaving an anchor at a distal end thereof; coupling the malleable memberto the exterior side of the reinforcement spring; and dipping themandrel into the plastic material to coat the mandrel with a secondlayer of the plastic material.
 43. The method of claim 42, wherein themalleable member comprises a wire slidably disposed within a tube. 44.The method of claim 43, wherein the anchor is a collar constructed of aflattened portion of the tube and wherein the wire does not extend intothe collar.
 45. The method of claim 43, wherein the anchor is a hookconstructed of a flattened portion of the tube and wherein the wire doesnot extend into the hook.
 46. The method of claim 43, wherein the anchoris a stepped portion constructed of a flattened portion of the tube andwherein the wire does not extend into the stepped portion.
 47. Themethod of claim 42, further comprising the step of injecting pressurizedalcohol into the mandrel to release the malleable cannula.
 48. Themethod of claim 42, wherein the plastic material is plastisol.
 49. Themethod of claim 42, wherein the malleable member is added to thereinforcement spring by using the liquid plastic material as anadhesive.
 50. A malleable cannula, comprising: a body having a proximalend and a distal end, the body having a wall defining a lumen extendingfrom the proximal end to the distal end; a reinforcement springextending along the lumen, the reinforcement spring having an interiorside facing the lumen and an exterior side facing away from the lumen;and a malleable wire extending along a portion of the exterior side ofthe reinforcement spring, the malleable wire having a U-shape, the lowerportion of the U-shape disposed at the distal end of the body.
 51. Amalleable cannula, comprising: a body having a proximal end and a distalend, the body having a wall defining a lumen extending from the proximalend to the distal end; a reinforcement spring extending along the lumen;and a malleable wire extending along the interior side of thereinforcement spring; wherein the reinforcement spring has a pluralityof loops, each loop having an outwardly bowed portion shaped toaccommodate the malleable wire between the reinforcement spring and thelumen without impacting the cross-sectional area of the lumen.